SQL Expression
Instructions for use
Structured Query Language (SQL) is a database query and programming language used for accessing data, as well as querying, updating, and managing relational database systems. In many scenarios, such as field expressions for thematic maps, filter expressions for data export, and field expressions for updating columns, SQL Expression can be used to perform operations on the fields of the selected dataset to obtain the desired results.
Parameter description
- Field: Displays the fields of the selected dataset.
- Join Attribute: Click this button to pop up the Join Attributes dialog, allowing you to connect external tables through associated fields, thereby enabling the construction of SQL Expression involving fields from external tables.
- Unique Value: Click the Get Unique Value button below Unique Value to list the unique values of the selected field here.
- Expression: Expression management tool, from left to right: Import, Export, Clear, function.
- Import: Imports an *.xml file containing expression information, and the expression input box below will be automatically filled with the corresponding information.
- Export: After setting up the expression, you can export it to an *.xml file for reuse.
- Clear: Clears all content in the current expression input box.
- function: Organizes function information that may be used in SQL Expression. For details, refer to SQL Query Function Description.
Note:SQL Expression supports switching between two different interface styles: new and old, with the new interface as the default. To switch to the old interface, follow these steps:
- Locate and open the EnvironmentSetting.xml file in the configuration folder under the program installation directory.
- Modify the useOldSQLExpressionDialog value to true, and save the file.
- Restart the program, and the SQL Expression interface will switch to the old version.
Related Topics
Common Expressions for Building SQL Query
SQL Query Function Description